1. Field of the Invention
The present invention relates in general to pneumatic therapeutic devices and in particular to an electronic circuit for a pneumatic control system for controlling a dynamic pressure wave device.
2. Description of the Prior Art
In the field of medical treatment, it is known that the application of pressure is helpful in the treatment of edema of the extremities as well as in the therapeutic prophylaxis for the prevention of deep vein thrombosis. There are two general types of pneumatic appliance systems known in the prior art for such treatment. One system utilizes a single chamber appliance to provide uniform compression of the extremity. The second system, often referred to as a sequential compression system, utilizes an appliance made up of a series of chambers or segments. In use, a sequential device inflates these appliance chambers one at a time, starting from the end of the appliance surrounding the most distal portion of the extremity until all of the chambers are inflated. Some inflation devices inflate all of the chambers to a uniform pressure while other devices inflate the most distal chamber to the highest pressure and subsequent chambers to a progressively lower pressure, thereby causing a pressure gradient. In all of the above-described devices, a pneumatic control system is electrically or mechanically operated to provide the desired results.
U.S. Pat. No. 4,106,002 discloses a tourniquet pressure monitor including an alarm which is actuated by a low pressure sensor or a high pressure sensor when the tourniquet pressure falls below or rises above a predetermined minimum or maximum interval, respectively, and an elapsed time indicator providing a visual indication of the total time during which the tourniquet has been pressurized.
U.S. Pat. No. 4,186,732 discloses an intermittent pressure device which is inflated from a source of compressed air to a pressure peak with a quick rise time. A generally constant plateau pressure is maintained by a pressure relief valve which permits excess air to escape from the compressor. At the end of the pressure cycle, a portion of the air is forced out of the device through connecting tubing as the patient's leg expands back to its normal size. Air in the device remains at atmospheric pressure until the next pressure cycle. Actuation of the above cycle is controlled by a pulse timer and a delay timer coupled together for operating the compressor, two three-way valves, and a rise time valve provided with a preset pressure relief valve set at the desired plateau pressure. The pulse timer actuates a flip flop relay to alternate the pressure cycle to either the right or left leg.